Process for manufacturing metallic filaments for incadescent electric lamps and for other purposes.



. UNITED STATES PATENT OFFICE.

KWAN NISHIMOTO, 0F TOKYO, JAPAN.

PROCESS FOR MANUFACTURING METALLIC FILAMENTS FOR INCANDESCENT ELECTRIC LAMPS AND FOR- OTHER PURPOSES.

No Drawing.

To all whom it may concern:

Be it known that I, KWAN Nisnnio'ro, a subject of the Empire of Japan, residing at No. 5 Minamikaji Cho, Kyobashi Ku, Tokyo, Japan, have'invented new and useful Improvements in Processes for Marinfacturing Metallic Filaments for Incandescent Electric Lamps and for other Purposes, of which the following is a specification.

My invention relates to a process for manufacturing coldly drawn metallic filaments for use in incandescent electric lamps and for other purposes.

Forming at first a consolidated stick ofa mixture of tungsten and a little proportion of thorium, both in a finely divided pulverulent state and chemically pure, rendering it an alloy by means of pressing, uniformly heating this said mixture at a sintering temperature by an electric current, and then gradually cooling its' temperature and keeping its temperature at dull red heat,

the consolidated stick is subjected to repeated mechanical manipulation, such as hammering or rolling, until it becomes so ductile that it may be hammered into bars, rolled into sheets, or drawn through dies into wires, much like the metals which are commonly treated in this manner at ordinary temperature. I have found also that, if this said alloy is uniformly. heated at a sintering temperature by an electric current as mentioned above and cooling is -allowed to proceed very slowly until it'becomes entirely cold, then the ductility is equally attainable to that obtained by the only means of this said repeated mechanical manipulation given thereon.

The objectof my invention is to obtain good filament of especially high efficiency, of long durability, and of strong resistibility to any vibration or shock that comes from flying machines or the like, for use in incandescent electric lamps and for other purposes. 1

In carrying the present invention into practical'efi'ect, a mixture'of tungsten and a small proportion of thorium. (about 5 per cent. of thorium), both in a finely divided pulverulent state andchemically pure, may

- be consolidated into sticks by'the'application of pressure. Inthis case the mixture is submitted to heavy pressure in a suitable mold, which may be of cast iron-or steel and should be highly polished, .and may be lubricated Specification of Letters Patent.

, come much Patented Oct. 1'7, 1916.

Application filed May 21, 1915. Serial No. 29,485.

they have just about enough strength to hold together. I then place them in a gasheated iron tube-furnace through which hy drogen is passed. The sticks may be inclosed in ironboats and packed about with powdered silica. This heating of the sticks may be about 1200 degrees centigrade in temperature and continued for-about two hours.

)uring this operation the lubricant, water,

'ammonia water, or oil, distils off, the occluded gas is driven off in vacuum and the carbon residue is removed by the current of hydrogen, and the sticks shrink and be stronger. Said metal sticks should, therefore, be first fused for which purpose they may be raisedin temperature very near their melting point, that is to say sintering temperature, by passing anelectric current through them in a vacuum or in an indifferent atmosphere. In this case this said metal stick should be uniformly, through its whole length, heated by an electric current. For instance this said stick is mounted in a large treating bottle filled with hydrogen and subjected to an electric current. This treatment should continue for 10 minutes in bright white heat and sinters to a dense hard. coherent stick, brittle at ordinary temperature.

I will next proceed to set forth a certain procedure, which may be carried out in connection with such coherent stick in accordance with my invention. Starting with a coherent stick of a mixture of tungsten and thorium, as mentioned above, the coherent stick is again heated a few minutes at a sintering temperature by passing an electric current through its whole length in vacuum or in an indifferent atmosphere, to allow the stick to cool slowly and then, keeping its temperature in dull red heat, mechanical manipulation, such as hammering or rolling action, is repeatedly given to it until it becomes so ductile that it may be hammered into bars, rolled into sheets, or drawn through dies into wires, much like the metals which .are commonly treated in this manner at ordinary temperature. The sintering cur- 3 rent may be continued in any event until the metal stick has been thoroughly and evenly sintered or consolidated into a very dense and homogeneous form. If this said metal stick.

- 'said metal stick, when it finally becomes cold, is very greatly increased. This efi'ect makes the alloy equally ductile at room temperature to that capable to be obtained by the only means of repeated mechanical manipulation given thereon. This alloy .is, therefore, so ClllCtilG'IthiLt it may be hammered into bars, rolled into sheets, or drawn through dies into wires.

By this present invention the ductile metal or alloy is in the form of drawn wire from this said metal or alloy in cold state, and the said metal or alloy so drawn has the-special effects of great ductility, of long durability, and of strong resistibility for any vibration or shock in a flying machine or the like, much like coldly drawn tantalum wires. The economical consumption of electrical energy namely, one watt of electrical energy per candle power is sufficient for the lamps of this filament, while one and quarter watts or the more is needed for the lamps of other wire provided.

Having thus described my invention, what I claim is:

1., The process of manufacturing metallic filaments for use in incandescent electric lamps and for other purposes, which consists in agglomerating a'mixture of tungsten and a small proportion of thorium, both in a finely divided pulverulent state and chemically pure, into a consolidated stick by press ing then' heating such stick at a sintering temperature by means of an electric current, and finally causing such stick to cool "ery slowly, at the same time reducing the electric current step by step.

2. A process for manufacturing metallic filaments for incandescent electric lamps and other" purposes, which consists in taking a mixture oftungsten and thorium in a finely divided state, consolidating the mixture into sticks by theapplication of pressure, heating the sticks so formed to sintering temperature by means of an electric current, allowing the sticks to cool slowly and then, while keeping the temperature at a dull red heat, submitting the sticks to repeated mechanical manipulation, such as hammering or rolling, and in subjecting such sticks to a drawing process, for the purpose hereinbefore set forth. v

3. A process for manufacturing metallic filaments for incandescent electric lamps and otherpurposes, which consists in taking a mixture of tungsten and thorium in a finely divided state, consolidating the mixture into sticks by the application of pressure, heating the sticks so formed tosintering temperature by means of an electric current and allowing the cooling to proceed slowly, at the same time reducing the current step by'step, and in subjecting such sticks to a drawing process, for the purpose hereinbefore setforth.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses. a

- KWAN NISHIMOTO. Witnesses: GENJI KUSIBARA,

' M. V. KASAWA. 

